We have studied transesterification of Rice bran oil with heterogeneous catalyst and found that the heterogeneous catalyst Mg-SO42-/ZrO2 worked very well for transesterification of oils. The maximum conversion was above 90% at Temperature 800C and the GCMS analysis of biodiesel showed that the biodiesel consisted of ten major products viz. Methyl Palmitate, Methyl Stearate, Methyl Oleate, Methyl Linolenate, Methyl Linoelate, Methyl Eicosanonate, Methyl Archidate, Methyl Tetra deconate, Methyl Pentyl hexonate and Methyl Behenate. The first order plots were found to be fit the conversion versus time data. Along with this yield of different components of the biodiesel versus time data showed the reaction is first order. It is also found that the the value of rate constant approximately 1 min-1. We have also purposed the reaction mechanism of biodiesel formation and explain with the results. The catalyst was characterized by FTIR, TGA, BET and SEM and we used this catalyst continuously for 1000 hours of reaction time without effecting conversion and yield which shows the catalyst activity remained unchanged at least for 1000 h. Therefore this catalyst can be used to produce biodiesel at industrial scale.